Next.js 13 introduced a revolutionary feature: the App Router. Built to enhance performance, scalability, and developer experience, it simplifies the routing system while adding flexibility for modern web development.

In this blog, we'll dive into how to use the App Router in Next.js, complete with code snippets and best practices.

Introduction to the App Router

The App Router replaces the pages directory with an app directory, making routing more intuitive and offering additional features such as layouts, server components, and nested routes.

Key benefits:

Enhanced support for React Server Components.
Simplified nested layouts.
Improved data-fetching capabilities.

Setting Up the App Router

To start with the App Router, ensure you have Next.js 13 or later installed. Here’s how to create a new project:

npx create-next-app@latest my-next-app --experimental-app
cd my-next-app

The --experimental-app flag sets up the app directory by default.

Your project structure will look like this:

my-next-app/
├── app/
│ ├── layout.js
│ ├── page.js
├── public/
├── styles/
├── package.json
└── next.config.js

Defining Routes

Each file in the app directory defines a route. By default, page.js files are used as route handlers.

Example:

app/page.js → /
app/about/page.js → /about

app/page.js:

export default function Home() {
  return <h1>Welcome to the Home Page</h1>;
}

app/about/page.js:

export default function About() {
  return <h1>About Us</h1>;
}

Visit / and /about in your browser to see the respective pages.

Dynamic Routing

Dynamic routes are defined by wrapping file names in square brackets.

Example:

app/blog/[slug]/page.js → /blog/:slug

app/blog/[slug]/page.js:

export default function BlogPost({ params }) {
  return <h1>Blog Post: {params.slug}</h1>;
}

When visiting /blog/my-first-post, the output will be:

Blog Post: my-first-post

Layout and Nested Routes

The App Router introduces the concept of layouts for consistent UI components like headers and footers.

File structure:

app/
├── layout.js
├── about/
│   ├── page.js
│   └── layout.js

app/layout.js:

export default function RootLayout({ children }) {
  return (
    <html lang="en">
      <body>
        <header>My Website</header>
        {children}
      </body>
    </html>
  );
}

app/about/layout.js:

export default function AboutLayout({ children }) {
  return (
    <div>
      <aside>About Sidebar</aside>
      {children}
    </div>
  );
}

Now, pages under /about will render with a sidebar.

Server Components

The App Router uses React Server Components by default, enabling faster rendering by offloading work to the server.

Example:

export default async function Products() {
  const res = await fetch("https://api.example.com/products");
  const products = await res.json();

  return (
    <ul>
      {products.map((product) => (
        <li key={product.id}>{product.name}</li>
      ))}
    </ul>
  );
}

Server-side data fetching is simple and efficient.

By leveraging the App Router, you can create scalable, performant, and maintainable Next.js applications with ease.

Happy coding!

Mastering Next.js App Router: A Deep Dive

SyncOps

Introduction to the App Router

Setting Up the App Router

Defining Routes

Dynamic Routing

Layout and Nested Routes

Server Components

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